How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Tim West Your Own Question
Tim West
Tim West, ASE Certified Technician
Category: Chevy
Satisfied Customers: 4638
Experience:  ASE Certified Service manager of Firestone
Type Your Chevy Question Here...
Tim West is online now
A new question is answered every 9 seconds

2002 Blazer will crank but not start... fuel pump is working

This answer was rated:

2002 Blazer will crank but not start... fuel pump is working
Thanks for visiting
Because the fuel pump turns on does not mean it's producing enough fuel pressure to start the car. Try spraying some carb cleaner in the throttle while cranking and see if the vehicle starts.
Also, is there a check engine light on?
Let me know if the vehicle will start on the extra fuel.
Customer: replied 7 years ago.
Sprayed the crb cleaner in there and yes there is a CIL on. but i noticed that i dont need my triad card to crank the engine. that is wierd
So did the engine start with the extra fuel?
Customer: replied 7 years ago.

No it did not start. it trys to catch but nothin. scratch the triad thing i do have to use my card.


A few days ago it did this after i had it on jacks changing out the ball joints. However after putting it in neutral and opening up the choke it started and ran rough for a few minutes. then everything was fine for two days. Then i go to start it this morning and all it does is crank with an occassional snort.

The plug wires one by one from th plug and see if you are getting spark. Dont shock yourself.
Customer: replied 7 years ago.
they seem to all have spark. the only one i cant get to is the one behind the steering column
Okay that's good, let's measure the fuel pressure can you do that?
Customer: replied 7 years ago.

No i dont have a fuel pressure gadge. I may have to buy one. But check this out:


I just did a tune up last spring and I pulled my ditributor cap off and the contacts have black/green build up. is that normal? after only around 8 months?

black and green? that doesn't sound right. You have spark now, you really need to find out if that fuel pump is building pressure and holding it.
Customer: replied 7 years ago.
ok ill have to go get a pressure gadge? and i hooks to the line going into the manifold?
That's right 60-66psi.
Customer: replied 7 years ago.
Ok that was expensive but it is holding at 60psi.
So you have good fuel pressure and good spark and the vehicle is still not starting?
Do you know what code is stored from the check engine light?
Customer: replied 7 years ago.
Unfortunately no. I do not have a code reader... maybe I can rent one at autozone
That might be the best idea, this is a tough one.
Customer: replied 7 years ago.
This is a tough one. I went a bought an actron ODB II and it doesnt even come on. I checked it on my wife toyota and it works
And the engine light is on?
No communication?
It might be a bad pcm if you cannot get the computer to communicate with the scan tool.
Tim West, ASE Certified Technician
Category: Chevy
Satisfied Customers: 4638
Experience: ASE Certified Service manager of Firestone
Tim West and 7 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.
Not what I wanted to hear Tim! If the pcm doesnt work it would screw all of the timing and smog equipment up correct? Whats that gonna run me and is it a do it your self thing
lol... aww man I know. You know what, let's get a second opinion. I will opt out so another expert can assist. If you think of anything new let me know and I will too.
Customer: replied 7 years ago.
No dont opt out.... i think your right man. Its looking like it pretty easy to change and not as much as i expected. And it makes sense. It snorts like the timing is off , it has plenty of fuel and spark. when it would start to have problems the check engine lihght would come on and then go out. Im gonna give it a shot
well, shouldn't be too hard to replace my manual does not mention a relearn for it either.
Customer: replied 7 years ago.
Gonna go for it. Hope this works thanks for all the help
Customer: replied 7 years ago.
Bummer the dealer says it has to be programmed so thats where they will get me lol
Well check the grounds of the pcm, thanks for the accept by the way.
Customer: replied 7 years ago.
I dont have anyway of checking the grounds. I have a voltmeter but not sure where to check
even knock on it. I am serious, I had a car with a bad pcm I hit the sun of a gun and the car started, true story.
Hey, I was talking to another mechanic about this one, he suggests a couple things:
There might be a crank in the distributor cap due to the green stuff.
Customer: replied 7 years ago.

I replaced the cap since it was the cheapest. But I did notice that when I took out my PCM and then tried to start it I had the same result. Is there a fuse or relay that might be bad that would stop the pcm from getting power?



ok,,lets not get a computer just yet,,,first check all fuses..then lets connect your fuel pressure gage ,,let your help turn the engine,,make sure the pressure don't drop below 60psi at all times..if the pressure drops down while cranking,you will need a fuel pump,,,,also,lets replace the rotor under the cap,,these rotors will sometimes burn a small pin hole in them and will short out,but will have some spark on the wires

let me know what happens..please print and use the info below


please ACCEPT my answer so I can get credit for my work.i don't receive commission unless you do ..i'm not always going to be giving you good news,so please don't let this stand in the way of you accepting my does not cost you more money.we will still be able to communicate.. Bonuses and positive feedback are appreciated!if you are not satisfied with my answer,please do not leave bad feed back,i will gladly opt out and let another expert handle the question.PLEASE ASK IF YOU NEED MORE HELP

fuel pressure

Testing and Inspection

When you turn ON the ignition, the vehicle control module Vehicle Control Module (VCM) energizes the fuel pump relay which powers the fuel pump ON. The pump remains ON as long as the engine is cranking or running and the VCM receives reference pulses. If there are no reference pulses, the VCM shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops. The VCM also turns ON the fuel pump for 2 seconds when you turn OFF the ignition.

An electric fuel pump pumps the fuel through an in-line filter to the fuel meter body assembly. The pump attaches to the fuel level sender assembly inside of the fuel tank. The fuel pump provides fuel pressure above what is needed by the fuel injectors. The pressure regulator keeps the fuel available to the injectors at a regulated pressure. Unused fuel returns to the fuel tank by the fuel return pipe.

Diagnostic Chart (Part 1 Of 5)
Diagnostic Chart (Part 2 Of 5)
Diagnostic Chart (Part 3 Of 5)
Diagnostic Chart (Part 4 Of 5)
Diagnostic Chart (Part 5 Of 5)

The numbers below refer to the step numbers on the diagnostic table.


  1. When the ignition is ON and the fuel pump is running, the fuel pressure indicated by the fuel pressure gauge should read 414-455 kPa (60-66 psi ). The spring pressure inside the fuel pressure regulator controls the fuel pressure.
  2. A fuel system that drops more than 34 kPa (5 psi ) in 10 minutes has a leak in one or more of the following areas:
    • The fuel pump check valve
    • The fuel pump flex pipe
    • The valve or valve seat within the fuel pressure regulator
    • The fuel injectors
    • A fuel pipe
  1. A fuel system that drops more than 14 kPa (2 psi ) in 10 minutes after being relieved to 69 kPa (10 psi ) indicates a leaking fuel pump check valve.
  2. Fuel pressure that drops-off during acceleration, cruise or hard cornering may cause a lean condition. A lean condition can cause a loss of power, surging, or misfire. You can diagnose a lean condition using a scan tool. If an extremely lean condition occurs, the heated oxygen sensors will stop toggling. The heated oxygen sensor output voltages will drop below 300 mV . The fuel injector pulse width will increase. IMPORTANT: Make sure the fuel system is not operating in the Fuel Cut-Off Mode. This can cause false indications by the scan tool.
  3. When you open the throttle quickly, the manifold pressure increases (low vacuum). The fuel pressure regulator increases the fuel pressure as the engine vacuum drops in order to compensate for engine load.
  1. A rich condition may result from the fuel pressure being above 455 kPa (66 psi ). A rich condition may cause a DTC to set. Driveability conditions associated with rich conditions can include hard starting followed by black smoke and a strong sulfur smell in the exhaust.
  2. This test determines if the high fuel pressure is due to a restricted fuel return pipe or if the high fuel pressure is due to a faulty fuel pressure regulator.
  1. A lean condition may result from the fuel pressure being below 414 kPa (60 psi ). A lean condition may cause a DTC to set. Driveability conditions associated with lean conditions can include hard starting (when the engine is cold), hesitation, poor driveability, lack of power, surging, and misfiring. NOTE : Do not. allow the fuel pressure to exceed 517 kPa (75 psi ). Excessive pressure may damage the fuel pressure regulator.
  2. Restricting the fuel return pipe with the fuel pipe shut-off adapter causes the fuel pressure to rise above the regulated fuel pressure. Using a scan tool to pressurize the fuel system, the fuel pressure should rise above 455 kPa (66 psi ) as the valve on the fuel pipe shut-off adapter connected to the fuel return pipe becomes partially closed.
  1. If the injectors are not grounded, check the spark plug associated with a particular fuel injector for fouling or saturation in order to determine if that particular fuel injector is leaking. If checking the spark plug associated with a particular fuel injector for fouling or saturation does not determine that a particular fuel injector is leaking, use the following procedure:
  1. Remove the fuel meter body assembly. Refer to Fuel Meter Body Assembly Replacement
  2. Reinstall the engine compartment fuel feed and return pipes to the fuel meter body and the chassis fuel pipes. Refer to Fuel Hose/Pipes Replacement (Engine Compartment).
  3. Lift the fuel meter body assembly just enough to leave the fuel injector poppet nozzles in the ports.
  4. Pressurize the fuel system by using the scan tool fuel pump enable.
  5. Visually and physically inspect the fuel injector poppet nozzles for leaks.
Engine Cranks, But Will Not Run


Diagnostic Chart
Enhanced Ignition System

Circuit Description

This table assumes that the battery condition and the engine cranking speed are OK, as well as having adequate fuel in the tank.

Diagnostic Aids

If no trouble is found in the fuel pump circuit or the ignition system and the cause of an Engine Cranks But Will Not Run has not been found, check for the following conditions:


  • Fouled spark plugs
  • An EGR valve stuck open
  • Low fuel pressure.
  • Water or foreign material in the fuel system
  • A grounded Ignition Control (IC) signal circuit may cause a No Stan or a Start then Stall condition
  • Basic engine problem

The Vehicle Control Module (VCM) has integrated IC circuits that are fault protected; therefore, if a circuit has failed, the integrated IC may not be damaged. If that is the case, the IC will keep the circuit open until the fault in the circuit has been corrected.

When the fault has been corrected, reinstall the VCM and check the circuit. Replace the VCM only if the circuit is still inoperative.

Test Description

The numbers below refer to the step numbers on the diagnostic tables.

  1. If the signal is over 2.5 volts, the engine may be in the clear flood mode which will cause starting problems.
  2. If the engine coolant sensor is below -30°C, the VCM provides fuel for this extremely cold temperature which will severely flood the engine.
  1. Use the injector test lamp J 34730-350 in order to test the injector circuit. A blinking lamp indicates that the VCM is controlling the injector.
  2. Voltage at the spark plugis checked using the spark plug tester tool J 26792. No spark indicates a basic ignition problem.
  3. This test will determines if there is fuel pressure at the fuel injection unit and holding steady.